package com.zhentao.util;


import java.net.InetAddress;
import java.net.UnknownHostException;

/**
 * @ClassName: SnowflakIdGenerator
 * @Author: muhaoyang1
 * @Date: 2024/12/26 18:14
 * @Comment:雪花算法生成器
 */

public class SnowflakeIdGenerator {

    // 起始的时间戳
    private final static long START_STMP = 1480166465631L;

    // 每一部分占用的位数
    private final static long SEQUENCE_BIT = 12; // 序列号占用的位数
    private final static long MACHINE_BIT = 10;   // 机器标识占用的位数
    private final static long TIMESTAMP_BIT = 41; // 时间戳占用的位数

    // 每一部分的最大值
    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);

    // 每一部分向左的位移
    private final static long MACHINE_LEFT = SEQUENCE_BIT;
    private final static long TIMESTAMP_LEFT = SEQUENCE_BIT + MACHINE_BIT;

    private long machineId;  // 机器标识
    private long sequence = 0L; // 序列号
    private long lastStmp = -1L;// 上一次时间戳

    public SnowflakeIdGenerator() {
        this.machineId = getMachineId();
    }

    public SnowflakeIdGenerator(long machineId) {
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
        }
        this.machineId = machineId;
    }

    /**
     * 产生下一个ID
     *
     * @return
     */
    public synchronized long nextId() {
        long currStmp = getNewstmp();
        if (currStmp < lastStmp) {
            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
        }

        if (currStmp == lastStmp) {
            // 相同毫秒内，序列号自增
            sequence = (sequence + 1) & MAX_SEQUENCE;
            // 同一毫秒的序列数已经达到最大
            if (sequence == 0L) {
                currStmp = getNextMill();
            }
        } else {
            // 不同毫秒内，序列号置为0
            sequence = 0L;
        }

        lastStmp = currStmp;

        return (currStmp - START_STMP) << TIMESTAMP_LEFT // 时间戳部分
                | machineId << MACHINE_LEFT             // 机器标识部分
                | sequence;                             // 序列号部分
    }

    private long getNextMill() {
        long mill = getNewstmp();
        while (mill <= lastStmp) {
            mill = getNewstmp();
        }
        return mill;
    }

    private long getNewstmp() {
        return System.currentTimeMillis();
    }

    /**
     * 获取机器ID
     * 这里简单地使用IP地址的最后一位作为机器ID
     * 实际应用中可以根据实际情况调整
     *
     * @return
     */
    private long getMachineId() {
        try {
            InetAddress inetAddress = InetAddress.getLocalHost();
            byte[] ipAddress = inetAddress.getAddress();
            return ((ipAddress[ipAddress.length - 1] & 0xFF) % (MAX_MACHINE_NUM + 1));
        } catch (UnknownHostException e) {
            e.printStackTrace();
            return 0;
        }
    }

    public static void main(String[] args) {
        SnowflakeIdGenerator idGenerator = new SnowflakeIdGenerator();
        for (int i = 0; i < 10; i++) {
            System.out.println(idGenerator.nextId());
        }
    }
}